Food Allergies A Challenge for Current and Emerging Proteins

Transcription

1 Food Allergies A Challenge for Current and Emerging Proteins Steve L. Taylor, Ph.D. Food Allergy Research & Resource Program University of Nebraska 2018 Protein Trends & Technologies Seminar Itasca, IL

2 Food Allergies Food allergens are proteins Food allergies increasing in prevalence in U.S. and other developed countries; 15 million Americans have food allergy and 3 million have celiac disease Symptoms range from mild and transient to severe and life-threatening Potency is another key concern as exposure to trace amounts can provoke allergic reactions Abnormal responses of immune system

3 Food Allergy (Food Hypersensitivity) IgE-Mediated Exercise-induced Cell-Mediated Celiac Disease

4 Mechanisms of Mediator Release

5 The Big 8 Most Common Causes of Food Allergy (IgE-Mediated) Cows milk Egg Crustacea Fish Peanut Soybean Tree nuts Wheat Responsible for 90% of all food allergies globally

6 Allergenic Foods on Common Allergen Lists in Other Countries Sesame seed Mustard Celery Buckwheat Molluscan Shellfish Lupine Canada, EU, Australia/ New Zealand EU, Canada EU Japan, Korea Canada, EU EU

7 Why Do Certain Protein Sources Make These Allergen Lists? Clinically significant allergens true of the Big 8 but maybe not for all (celery, mustard in EU) Prevalence of allergy but good data are lacking Severity yes but hard to track Potency should be important Could my favorite new protein source end up on one of these lists? The lupine story

8 Characteristics of Commonly Allergenic Foods Frequently consumed Consumed in relatively large amounts Consumed in early life stages (with exceptions) Excellent sources of protein Allergenic sensitizing capacity of individual proteins in the food matrix

9 Factors Involved in Development of IgE- Mediated Food Allergy Sicherer and Sampson. J Allergy Clin Immunol. 2007; 120:

10 Could My Favorite Novel Food Protein Source Become Allergenic? Inevitable; reports of allergic reactions should not be a surprise But perhaps not commonly; prevalence will be predictable to some extent Not all adverse reactions will be allergic reactions Should not be a deterrent to development of new protein sources Clear labeling is the key

11 Could Novel Food Sources of Protein Become Allergenic? Soybean from obscurity to the Big 8 Quorn all reactions may not be allergies Lupine an unexpected surprise Pea protein lupine revisited?? Canola protein isolate - predictable Insects as foods Wheat protein isolate modifications can make a difference

12 Could Novel Food Sources of Protein Become Allergenic? Soybeans Quorn Lupine Pea protein Canola protein isolate Insects as foods Wheat protein isolate

13 Soybeans First domesticated in China in ~ 1100 BC Introduced in U.S. in 1765 But first widely grown in U.S. in 1940s due to WWII impacts on production in China First soy foods for humans were Asian origin: tofu, soy sauce, etc soy infant formula developed but more widely used in 1950s 1959 soy protein isolates first introduced

14 Soybean Allergy Prevalence increased from 1950s because milkallergic infants were fed soy formula and some developed allergy to soy Soy formula primary (sole) source of nutrition; soy primary source of protein Higher intake of soy protein from many sources in U.S. diet beginning in 1960s Most children outgrow soy allergy but still Big 8 Not a very potent allergenic food

15 Should Product Developers Still Worry About Soybean Allergy? Company introduced muscle-building beverage with very high levels of soy and milk protein Received multiple consumer complaints including 6 reports of severe reactions in peanut-allergic subjects No peanut residues in beverage Using sera from 4 of these subjects, FARRP determined that all were highly allergic to peanut and slightly allergic to soy Tentative conclusion: the beverage had enough soy protein to exceed threshold dose of these consumers

16 Could Novel Food Sources of Protein Become Allergenic? Soybeans Quorn Lupine Pea protein Canola protein isolate Insects as foods Wheat protein isolate

17 Quorn Mycoprotein or mycelial mass with high protein and fiber content Product release as Quorn in U.K. in 1985; GRAS approval in U.S. in 2001 Enjoys reasonable popularity in U.K. Adverse reactions reported by minority of consumers; most only with GI symptoms; likely due to individual problems in handling the high fiber content Handful of allergic reactions reported since 1985

18 Could Novel Food Sources of Protein Become Allergenic? Soybeans Quorn Lupine Pea protein Canola protein isolate Insects as foods Wheat protein isolate

19 Lupine A legume with at least 4 edible species but historically used mostly as cattle feed In EU, lupine flour and other lupine protein ingredients introduced as replacements for soy flour, isolate and concentrate In Australia, lupine flour and other lupine protein ingredients introduced as novel foods In EU principally, allergic cross-reactions were noted in some peanut-allergic individuals; not so common in Australia Lupine now on priority allergen lists in EU and Australia

20 Could Novel Food Sources of Protein Become Allergenic? Soybeans Quorn Lupine Pea protein Canola protein isolate Insects as foods Wheat protein isolate

21 Pea Protein Peas are a traditional legume crop eaten both as garden peas and as dry peas Pea protein ingredients developed recently and have surged in popularity in past several years Pea allergy from garden pea is rather rarely encountered but protein exposure is low Pea protein ingredients will serve to increase pea protein exposure Does pea protein cross-react with peanut? Analytical challenges

22 Could Novel Food Sources of Protein Become Allergenic? Soybeans Quorn Lupine Pea protein Canola protein isolate Insects as foods Wheat protein isolate

23 Canola Protein Isolate Canola is widely used as oil source but meal was not historically fed to humans due to presence of anti-nutrients Several companies have made canola protein isolate with no detectable anti-nutrients and usefuil technological properties Canola, rapeseed, and mustard are very closely related Mustard-allergic consumers are very likely to react to canola protein isolate

24 Could Novel Food Sources of Protein Become Allergenic? Soybeans Quorn Lupine Pea protein Canola protein isolate Insects as foods Wheat protein isolate

25 Insects as Food Insects (meal worm, silk worm, cricket, etc.) can serve as excellent sources of protein and other nutrients Yuck factor overcome by use of forms such as cricket flour Insects are invertebrates so concern about possible allergic cross reactions with other invertebrates, namely crustacean and molluscan shellfish Tropomyosin is a major allergen in shrimp but also exists in insects; cross-reactivity??

26 Could Novel Food Sources of Protein Become Allergenic? Soybeans Quorn Lupine Pea protein Canola protein isolate Insects as foods Wheat protein isolate

27 Wheat Protein Isolate During the Atkins Diet/low-carb period, many new, functional sources of proteins were developed Several variations of wheat protein isolates were introduced with differing technological functionality One wheat protein isolate introduced especially in EU as a coffee creamer Allergic reaction complaints surfaced, curiously among individuals who could eat wheat flour Most allergic reactions associated with one particular modified from of WPI; removed from market

28 Can We Predict the Allergenic Potential of Novel Food Sources of Protein? Is the food already known to be allergenic when consumed in more limited quantities? e.g. pea Is the food commonly allergenic in another country where it is more commonly consumed? e.g. buckwheat Is the food botanically related to known allergenic foods? e.g. soy, lupine, pea, insects Does the food contain a potentially cross-reactive protein? e.g. lupine

29 Prediction Examples Cottonseed protein severe allergy cases reported from limited consumption Canola protein very closely related to mustard Buckwheat commonly allergenic in Japan and Korea Lupine a legume (but there are 100s) Pea a legume (but there are 100s) Insects potentially cross-reactive protein with crustacean shellfish

30 Recommended Actions Search global clinical allergy literature for evidence of allergic reactions to the novel food Identify and assess allergenicity of botanically related species Determine abundance and amino acid sequence homology of individual proteins that are from the same class as major allergens from closely related sources Test for cross-reactivity and digestive stability

31 Predicting the Allergenicity of Individual Food Proteins Humans consume 1000s of plant and animal proteins in the diet on a daily basis; all dietary proteins are foreign proteins to the human immune system Only a small number of proteins from plant and animal origin cause an IgE-mediated immune response in only a small number of humans Oral tolerance is the homeostatic condition for dietary proteins Why are some proteins allergenic while others are not?

32 Why Are Some Food Proteins More Allergenic? Comparative abundance Usually major proteins of the food Heat-resistant Resistant to digestion/proteolysis Resistant to extremes in ph Foods can have 1 or many allergens in them

33 Characteristics of Food Allergens Abundance: Most of the major food allergens are present a levels >1% of the total protein in the food Immune system more likely to encounter abundant proteins Seed storage proteins are especially abundant IgE-binding epitopes: Most food allergens have multiple, linear epitopes and often these are arranged as conformational epitopes

34 Characteristics of Food Allergens Resistance to denaturation and digestion: Highly stable proteins have the opportunity to interact with immune system for longer periods Allergen structure: Secondary and tertiary structure may contribute to stability Many food allergens contain disulfide bonds that stabilize the protein structure Other allergenic food proteins form aggregates that enhance stability

35 Classification of Food Allergens Food allergens are commonly classified into families by their shared amino acid sequences and conserved 3-D structures Bioinformatics analysis indicates that the majority of food allergens from plant sources fall in 4 families Food allergens from animal sources fall within 3 main families

36 Classification of Food Allergens 4 main families of plant-based food allergens: Prolamin superfamily Cupin superfamily Bet v 1 family Profilins 3 main families of animal-based food allergens Tropomyosins EF-hand proteins Caseins

37 Prolamin Superfamily Characterized on the basis of the presence of a conserved 8 cysteine amino acid residue pattern CX n CX n CCX n CXCX n CX n C Stabilizes protein structure which contributes to overall allergenicity of proteins in this class (highly resistant to heating, proteolysis and digestion) Share a common 3-D structure consisting of bundles of 4 α- helices stabilized by disulfide bonds Includes cereal prolamins, 2S albumins, non-specific lipid transfer proteins, and α-amylase and trypsin inhibitor protein families

38 Prolamin Superfamily Gliadin Major seed storage protein from wheat Major component of gluten Involved in gluten sensitivity (celiac disease) Related proteins in barley, rye, triticale, spelt nsltps Facilitate transfer of phospholipids; plant defense against fungal and bacterial infections Mal d 3 (apple), Pru ar 3 (cherry), Pru p 3 (peach), Jug r 3 (walnut), Cor a 8 (hazelnut), Aspa o 1 (asparagus), Lac s 1 (lettuce), Bra o 1 (cabbage)

39 Prolamin Superfamily α-amylase/trypsin inhibitors Provide protection against degradative proteases produced by insect pests and pathogens Rag 1, 2, 5 (rice) 2S albumins Seed storage proteins Jug r 1 (walnut), Ber e 1 (Brazil nut), Ana o 3 (cashew), Sin a 1 (yellow mustard), Bra j 1 (black mustard), Ara h 2, 6, 7 (peanut), Ses i 2 (sesame), SFA-8 (sunflower)

40 Prolamin Superfamily 2S Albumins: Seed storage proteins of dicotyledonous plants Synthesized as single chains of kda Many post-translationally processed into small and large subunits joined by disulfide bonds Peanut and sunflower are not modified and remain as a single unit Ara h 2 has some trypsin inhibitor properties Ara h 2

41 Prolamin Superfamily 2S Albumins: Major allergens in peanut, mustard, sesame seed, walnut, cashew, sunflower seed Involved in provocation of severe allergic reactions Ara h 2

42 Novel Legume Source Recommended Approach Expression level of 2S albumin?? soy vs. peanut Amino acid sequence homology with Ara h 2 from peanut?? Ability to provoke mediator release from basophils armed with IgE antibodies of peanutallergic individuals??

43 Tropomyosin Superfamily Tropomyosins are a family of closely related proteins present in all eukaryotic cells Play a key role in regulation of muscle contraction Major allergens in crustacean and molluscan shellfish Pen a 1 (shrimp), Cha f 1 (crab), Tod p 1 (squid), Hal d 1 (abalone), Cra g 1 (oyster), Hel as 1 (snail) Inhalant allergen from mites and cockroaches Minor inhalant allergen in most societies

44 Tropomyosin Superfamily Only non-vertebrate tropomyosins have been identified with allergenic activity Differences in the IgE binding epitopes in the C-terminal portion of tropomyosin results in no cross-reactivity to vertebrate tropomyosin Of those that are allergenic, they have been shown to be highly cross-reactive Resistant to heat and digestion Tropomyosins are water soluble and can withstand boiling

45 Novel Insect Source Recommended Approach Likely to express invertebrate tropomyosin Amino acid sequence homology with shrimp tropomyosin?? Ability to provoke mediator release from basophils armed with IgE antibodies of shrimpallergic individuals??

46 Conclusions & Recommendations Novel food sources of protein will inevitably be allergenic Thus, be careful about marketing these foods as non-allergenic It is more accurate to state that these food sources contain no commonly allergenic food But be careful of potential for cross-reactivity with commonly allergenic foods

47 Conclusions & Recommendations Novel food regulations in Canada and EU will require assessment of allergenic potential Be cautious in U.S. and other countries where the regulatory path forward on novel foods is unclear; you might simply get blocked Example: lupine in the U.S.

48 Conclusions & Recommendations Allergenic potential should not be a deterrent to marketing of novel food protein sources Clear labeling is the key With clear labeling, those consumers who develop allergic reactions will be able to avoid the food Preventive allergen controls will allow management of allergen risks within manufacturing facilities

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